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Invasive cheatgrass fuels bigger, more frequent wildfires

December 05, 2012|Bettina Boxall
  • A cheatgrass-choked hillside near the Snake River Birds of Prey National Conservation Area in Idaho
A cheatgrass-choked hillside near the Snake River Birds of Prey National… (Brian VanderBrug / Los Angeles…)

When a team of academic researchers blended wildfire data with satellite images from the Great Basin, they confirmed what public land managers and ranchers have seen on the ground for years: cheatgrass, an invasive grass accidentally introduced by settlers more than a century ago, is fueling bigger, more frequent wildfires in that empty stretch of the West.

Comparing regional land cover maps with the dates and boundaries of Great Basin wildfires, the researchers found that fires in areas dominated by cheatgrass consistently ranked as the largest or second largest. Of the 50 biggest fires recorded in one dataset from 2000 to 2009, 39 involved cheatgrass. The invasive covered 6% of the landscape, but 13% of the burned land, giving it an outsized role in the largest fires.

Cheatgrass-covered rangelands were also nearly four times more likely to burn during that period when compared with all land with native vegetation, according to the study, which appears in the current online edition of Global Change Biology.

Cheatgrass-driven changes in the wildfire cycle are destroying the sagebrush ecosystem in big stretches of the Great Basin, which includes most of Nevada and parts of Utah, Idaho, Oregon and California.

A short-lived annual that is dead most of the year, the exotic grass doesn’t provide the nutrients or wildlife shelter that natives do, ultimately stripping land of its biodiversity.

It ignites easily and burns quickly, fueling fires that incinerate sagebrush, pinyon-juniper woodlands and other native plants. “As sites burn, more and more of them are likely to become cheatgrass grasslands, thus increasing their future probability of burning,” wrote the study authors, who were from Penn State, the University of Massachusetts-Amherst, UC Santa Barbara and University College London.

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